Thyroid nodules are lumps which commonly arise within an otherwise normal thyroid gland. They indicate a thyroid neoplasm, but only a small percentage of these are thyroid cancers.
Often these abnormal growths of thyroid tissue are located at the edge of the thyroid gland and can be felt as a lump in the throat. When they are large or when they occur in very thin individuals, they can sometimes be seen as a lump in front of the neck. Sometimes a thyroid nodule presents as a fluid filled cavity called a thyroid cyst. Often, solid components are mixed with the fluid. Thyroid cysts most commonly result from degenerating thyroid adenomas, which are benign, but they occasionally contain malignant solid components.
After a nodule is found during a physical examination, most commonly an ultrasound is performed to confirm the presence of a nodule, and assess the status of the whole gland. Measurement of thyroid stimulating hormone and anti- thyroid anti- bodies will help decide if there is a functional thyroid disease such as Hashimoto’s thyroiditis present, a known cause of a benign Nodular goiter. Fine needle biopsy for histopathology is also used. Thyroid nodules are extremely common in young adults and children. Almost 50% of people have had one, but they are usually only detected by a primary care physician during the course of a health examination, or through a different affliction.
Fine needle biopsy:
One approach used to determine whether the nodule is malignant is the fine needle biopsy (FNB), which some have described as the most cost- effective, sensitive and accurate test. FNB or ultrasound- guided FNA usually yields sufficient thyroid cells to assess the risk of malignancy, although in some cases, the suspected nodule may need to be removed surgically for pathological examination.
Blood or imaging tests may be done prior to or in lieu of a biopsy. The possibility of a nodule which secrets thyroid hormone ( which is less likely to be cancer ) or hypothyroidism is investigated by measuring thyroid stimulating hormone ( TSH ), and the thyroid hormones thyroxine ( T4 ) and triiodothyronine ( T3 ). Tests for serum thyroid autoantibodies are sometimes done as these may indicate autoimmune thyroid disease (which can mimic Nodular disease).
The blood assays may be accompanied by ultrasound imaging of the nodule to determine the position, size and texture, and to assess whether the nodule may be cystic (fluid filled). Also suspicious findings in a nodule are hypoechoic, irregular borders, microcalcifications, or very high levels of blood flow within the nodule. Less suspicious findings in benign nodules include hyperechoic, comet tail artifacts from colloid, no blood flow in the nodule and a halo or smooth border. Nuclear medicine can be used to image the thyroid with radioactive technetium (Tc) or iodine (I) imaging of thyroid. A 123 I scan showing a hot nodule, accompanied by a lower than normal TSH, is strong evidence that the nodule is not cancerous.
Only a small percentage of lumps in the neck are malignant (around 4-6.5%), and most thyroid nodules are benign. There are many factors to consider when diagnosing a malignant lump. Trouble swelling or speaking, swollen cervical lymph nodes or a firm, immobile nodule are more indicative of malignancy, whereas a family history of autoimmune disease or goiter, thyroid hormonal dysfunction or a soft, painful nodule are more indicative of benignancy. The prevalence of cancer is higher in males, patients under 20 years old or over 70 years old, and patients with a history of head and neck irradiation or a family history of thyroid cancer. Solitary thyroid nodule:
Risks for cancer:
Solitary thyroid nodules are more common in females yet more worrisome in males. Other associations with neoplastic nodules are family history of thyroid cancer and prior radiation to the head and neck. Radiation exposure to the head and neck may be for Hodgkin’s lymphoma. Thyroid cancer arising in the background of radiation is often multifocal with a high incidence of lymph node metastasis and has a poor prognosis.
Signs and symptoms:
Worrisome signs and symptoms include voice hoarseness, rapid increase in size, compressive symptoms (such as dyspnoea or Dysphagia) and appearance of lymphadenopathy.
* TSH- A thyroid stimulating hormone level should be obtained first. If it is suppressed, then the nodule is likely a hyper functioning (“hot ” ) nodule. These are rarely malignant.
* FNAC- fine needle aspiration cytology is the investigation of choice given a non- suppressed TSH. Repeat the FNAC in 6 months if the nodule enlarges.
* Imaging- ultrasound and radiological scanning.
* Cold- 85% of nodules are cold. 5-8% of cold and warm nodules are malignant.
* Hot- 5% of nodules are hot. Malignancy is virtually non- existant in hot nodules.
Surgery is indicated in the following instances:
* Reaccumulation of the nodule despite 3-4 repeated FNACs.
* Size in excess of 4 cm in some cases.
* Compressive symptoms
* Signs of malignancy (vocal cord dysfunction, lymphadenopathy)
* Levothyroxine is a stereoisomer of thyroxine which is degraded much slower and can be administered once daily in patients with hypothyroidism.
Dr. A. K. M. Aminul Hoque
Prof. of Medicine
Dhaka Community Medical College & Hospital